1. Field
This invention is directed to an apparatus for lifting and placing heavy items in precise position for installation such as installing heavy mine belt roller assemblies which include, for example three heavy rollers mounted on a steel frame, as repair or for belt extensions or the like in underground tunnel mining operations.
In the field of underground mining, most mines transport material from the mining faces to the outside of the mine by means of belt conveyors. Even in shaft mines, conveyor belts usually transport the material to the shaft skips. As an example of one typical situation, as mining progresses, conveyor beltlines must be extended by installing conveyor belt, top run and return run idler rollers, and support structure therefor. In the higher production mines which have wider belts, larger and much heavier roller assemblies and frame structure are required to support the conveyor belts.
2. Prior Art
Heretofore, installing the roller assemblies, for example, has been very difficult for the workers, to the point of being a chronic safety issue. A single top roller assembly can weigh over 300 lbs. requiring four or more workers to lift and manipulate the assembly in precise mounting position on supporting rails of a conveyor. Medium size idler assemblies weighing 100 lbs. or so each are still a safety issue. A single back injury can cost a mining company over $500,000.
Installing the larger belt components is also a production efficiency issue. Work accomplished per hour in making an installation is slow, and considerable production can be lost due to the extended time required to make, for example, a belt advancement (extension). Needed for years has been a good mechanical means to lift, manipulate and precisely position the larger roller assemblies and frame structure to reduce difficulty, number of workers, man hours, injuries, and downtime encountered in the installation. Further, in the case of coal mining, which is the largest segment of underground mining in general, the tunnel width is limited, by law, to 20 feet. The belt lines are usually installed with the edge of the belt line on the center line of the shaft entry leaving a maximum of about 10 feet lateral space in which to accomplish a mechanical installation of roller assemblies or other structure. Also involved in developing a viable mechanical alternative to the human back is the limited vertical room to the mine roof such that large equipment may not fit into the shaft.